Stop adiftools import from overriding notebook matplotlib backend

adiftools/adifgraph.py

@@ -1,4 +1,3 @@
-import matplotlib
 import matplotlib.pyplot as plt
 import pandas as pd
 
@@ -7,8 +6,6 @@
 except ModuleNotFoundError or ImportError:
     from errors import AdifParserError
 
-matplotlib.use('Agg')
-
 
 def monthly_qso(df, fname):
     ''' plot monthly QSO '''

tests/test_adifgraph.py

@@ -1,3 +1,7 @@
+import importlib
+
+import matplotlib
+
 from adiftools import adiftools
 from adiftools import adifgraph
 
@@ -18,3 +22,15 @@ def test_band_percentage():
 def test_monthly_band_qso():
     adifgraph.monthly_band_qso(df, 'tests/monthly_band_qso.png')
     assert True
+
+
+def test_import_does_not_force_matplotlib_backend(monkeypatch):
+    calls = []
+
+    def spy_use(*args, **kwargs):
+        calls.append((args, kwargs))
+
+    monkeypatch.setattr(matplotlib, 'use', spy_use)
+    importlib.reload(adifgraph)
+
+    assert calls == []